Summary of Work: The purpose of this intra-agency agreement (Y02-AG-5- 0282) is to support the measurement of arterial pulse wave velocity (APWV) as a measure of arterial stiffness in the NHLBI Activity Counseling Trial (ACT). This portion of the trial was designed to test the hypothesis that increases in physical activity resulting from educational interventions will reduce arterial stiffness. The setting is appropriate for this hypothesis testing because of the prospective nature of the study and the range of interventions which have been adopted. The measurements were taken at three points in time when other physiologic measures were taken. This allows assessment of intra- individual variability as well as the possibility of examining change over time in these measures in relation to the level of compliance with the physical activity intervention. The study has taken place in three geographic locations to assure adequate sample size for subgroup analysis: Memphis, TN, Dallas, TX and Palo Alto, CA. Pulse wave velocity was measured by two Doppler flow velocity probes simultaneously measuring the carotid and femoral arteries. A computer algorithm calculated average flow velocity tracings on a beat-to-beat basis. The time needed for the pressure wave to travel from the proximal to distal sampling site was calculated from the foot of the pressure wave.The 24-month examinations have now been completed, with quality control reports from the Coordinating Center indicating that a sufficiently large proportion of the tracings are of acceptable quality and can be used for analysis. While the numbers of individual participants with readings at all three time periods is relatively small, there are sufficient numbers of persons with a baseline and at least one follow-up reading to permit longitudinal analysis to assess the effect of the intervention on the measures of stiffness. That part of the analysis will be continuing as the data from the 24-month follow-up are finalized.Analysis of the baseline data is now under way, and preparation of a baseline manuscript will be soon to follow. The computing work required for fitting statistical models to the baseline data is being conducted by the Coordinating Center. Preliminary analysis of the longitudinal data will be under way once the baseline analysis is completed. - assessment, measurement, arterial pulse wave velocity - Human Subjects